Change general fill rect shader code to match geometry vers

-Matches shader implemented for alligned rects
-Uses multiplication instead of min (used in geom version)
 to combine width and height coverages

R=bsalomon@google.com, robertphillips@google.com

Review URL: https://codereview.chromium.org/17035012

git-svn-id: http://skia.googlecode.com/svn/trunk@9626 2bbb7eff-a529-9590-31e7-b0007b416f81
1 file changed